1. Field of the Invention
The present invention relates to an apparatus and method of controlling a crane. More particularly, the present invention relates to an apparatus and method of controlling a refuse disposal crane which is used for lifting and moving refuse or solid wastes, including earth and sand in incinerator plants or at reclamation sites.
2. Description of the Related Art
The refuse disposal plant has a pit for temporarily storing the refuse, a furnace, a crane for lifting and moving the refuse from the pit to the furnace, and a crane controller.
The crane controller contains a level controller for controlling level data indicative of the height of a heap of the refuse accumulated in the pit. The level controller further contains a level memory for storing level data, a computer for computing a level of a piled refuse by using output data from sensors, for example, a position sensor and a load sensor, and device for updating the level data stored in the level memory.
In order to automatically operate the crane by using the level data stored in the level memory, it is important whether the level data stored in the level memory is proper reasonable or correct or improper.
One of the methods which can be used to check the properness of the level data is to check whether or not the level data is within a range between the upper limit and the lower limit, both preset. This approach is unsatisfactory. For example, when something is wrong with the load detector and/or the position detector, the level data difference between the adjacent places of the refuse heap becomes great. In such a case, the above approach cannot recognize the abnormality of the level data so long as the level data is between the upper and the lower limit values. A possible measure for this is that when that level data difference is great, the present level data are displayed on a monitor and an operator sees the display and judges whether the level data is proper or improper. This measure makes the operator's work increase and intricated. Under the condition of improper level data, the refuse disposal unsmoothly progresses and the incinerator plant insteadily operates.
The above problems may also be found in other facilities and plants using cranes.